The invention relates to a sharpening machine for saws. Machines of this sort generally include a support for a saw blade and a spindle head which carries a grinding wheel spindle for a dish-shaped grinding wheel. The spindle head is disposed on a lifting carriage. The lifting carriage is connected to a carrier and is rotatable about a swiveling axis which intersect the axis of the grinding wheel spindle. The spindle head may be placed in a standard position in which the axis of the grinding wheel spindle lies in the plane of the saw blade or parellel thereto, and from there swiveled around the swiveling axis. The carrier can be tilted by at least 90.degree. around a standard tilting axis which is normal in relation to the common plane of the axis of the grinding wheel spindle and the swiveling axis.
In the case of known sharpening machines of saws of this type, the swiveling range of the lifting carriage, starting out from the standard position in which the axis of the grinding wheel spindle lies in the plane of the saw blade, is between 30.degree. to 45.degree. in either direction. Swiveling like this is provided exclusively for the purpose of grinding surfaces on the teeth of the saw blade which are slanting toward the one or the other side and especially surfaces of the tooth face alternatingly slanting to the one or the other side.
The tilting range of the carrier lies between a position in which the axis of the grinding wheel spindle has been disposed in parallel to the feed direction of the saw blade and a position in which the axis of the grinding wheel spindle is disposed normally in relation to the feed direction of the saw blade. By shifting the carrier within the tilting area, it will be possible to grind the surfaces of tooth faces having any arbitrary rake angle and the surfaces of the teeth having any arbitrary setting angle. By rake angle is meant the angle between the straight line lying in the plane of the saw blade and at the same time in the surface of the tooth face, and a perpendicular line in relation to the feed direction or the direction of the operational movement of the saw blade. By a setting angle is meant the angle between the feed direction or the direction of operational movement of the saw blade and a straight line tangential to the surface of the rear of the teeth in the point of the tooth, lying in the plane of the saw blade. It is customary to arrange the plate-shaped grinding wheel for the grinding of the surfaces of the tooth face in such a way, that the operating surface of the grinding wheel studded generally with diamonds, faces the spindle of the grinding wheel. For grinding the rear surfaces of the teeth, said grind wheel on the contrary is customarily disposed in such a way, that its operating surface faces away from the spindle of the grinding wheel. In both cases, the spindle head is preferably disposed in such a way, that the swiveling axis of the lifting carriage extends through the operating surface of the grinding wheel and intersects the axis of the spindle of the grinding wheel at a right angle. The known tilting range of the carrier described, also suffices for the grinding of such saw blades, the rake angle of which is negative, as frequently happens for metal processing. The grinding of both positive as well as of negative rake angles is made possible in the case of known machines of the described variety by the fact, that the saw blade is mounted differently. For example, the blade of a circular saw with a positive rake angle is mounted in such a way, that the forward rotational direction of the saw blade is opposite to the clockwise direction. A saw blade of a circular saw with a negative rake angle on the contrary is mounted in such a way, that the forward rotational direction of the saw blade agrees with the clockwise direction. In the first mentioned case, the operating surface of the grinding wheel faces the spindle of said grinding wheel and in the second case, the operating surface of the grinding wheel faces away from the spindle of said grinding wheel.
The requirement of mounting saw blades with a negative rake angle differently from saw blades with a positive rake angle has not been felt to be disturbing hitherto. If however, in the case of a saw blade with a negative rake angle, not only the surfaces of the tooth face but also the rear surfaces of the tooth are to be ground, it is necessary in the case of known sharpening machines to reverse the saw blade after the grinding of the surfaces of the tooth face which may be very cumbersome in the case of large and heavy saw blades.
The invention is based on the object of designing a sharpening machine for saws of the initially described type in such a way, that all surfaces of the tooth face and the rear of the tooth and possibly additionally even the chamfers may be ground in every case with a single clamping of the saw blade no matter whether the rake angle is positive or negative.